A non-excavation geophysical exploration method for the position of fixed piers of directly buried heating pipelines

Abstract

The present invention provides a non-excavation geophysical prospecting method for the position of fixed piers of directly buried heating pipelines, which includes the following steps: Step 1: Apply voltage to the heating pipeline at the manhole, and measure the electric potential value on the ground along the energized heating pipeline route starting from the manhole to measure the high electric potential point; Step 2: Use a transient electromagnetic detector to measure the induced electromotive force at the high electric potential point. If the induced electromotive force at this high electric potential point is higher than the induced electromotive forces of the heating pipelines on both sides, then this high electric potential point is the buried position of the fixed pier. The present invention adopts the means of non-excavation geophysical prospecting and uses the method of electric inspection plus transient electromagnetic to find the fixed piers buried underground, which can eliminate the influence of factors such as pipeline damage and accurately locate the buried position of the fixed piers.

Description

Technical Field

[0001] The invention belongs to the technical field of non-excavation geophysical exploration for accessories of directly buried heating pipelines, and particularly relates to a non-excavation geophysical exploration method for the position of fixed piers of directly buried heating pipelines. Background Technique

[0002] In northern China, heating supply in winter is provided by centralized heating, and directly buried heating pipelines are a common pipeline laying method for the primary pipeline network of urban heating systems. In addition to the pipelines, accessories need to be installed for directly buried heating pipelines, and the accessories include compensators, fixed piers and valves. The primary pipeline network of urban heating systems supplies heat in winter, the temperature of the supply pipe is generally 95 - 135 °C, and the temperature of the return pipe is generally 30 - 40 °C. In summer, there is no heating, and the temperatures of the supply pipe and the return pipe are generally 15 °C. The temperature difference will cause changes in the pipeline expansion amount. In order to prevent the pipeline from bursting, compensators need to be installed. According to custom, a compensator is set every 50 meters. After installing a compensator on the pipeline, a creep effect will occur. In order to prevent the pipeline from having a creep effect, fixed piers need to be installed on the pipeline. According to custom, one is also set every 50 meters. The specific method is as follows: weld steel rings on the metal pipe of the pipeline to form a fixed section, then set up a steel cage formwork outside the fixed section, and finally pour concrete to seal the fixed section and the steel cage formwork inside the concrete to form a fixed pier.

[0003] The accessories need to be regularly inspected and replaced. Valves are generally installed in manholes, and their positions are easy to confirm. Compensators and fixed piers are buried underground together with the pipeline. In addition, due to limited early construction technology and large changes in the urban surface, early pipeline data are missing and inaccurate, making it difficult to determine the accurate buried position of the fixed pier. And using the method of fully excavating along the pipeline to find the fixed pier has the problems of long construction period and high cost. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the invention provides a non-excavation geophysical exploration method for the position of fixed piers of directly buried heating pipelines. By using the method of electrical inspection plus transient electromagnetic method to find the fixed piers buried underground, the influence of factors such as pipeline damage can be excluded, and the buried position of the fixed pier can be accurately located.

[0005] The technical solution adopted by the invention is: a non-excavation geophysical exploration method for the position of fixed piers of directly buried heating pipelines, including the following steps:

[0006] Step 1: Apply voltage to the heating pipeline at the manhole, and measure the electric potential value on the ground along the power supply heating pipeline route starting from the manhole to measure the high electric potential point;

[0007] Step 2: Use a transient electromagnetic detector to measure the induced electromotive force at the high potential point. If the induced electromotive force at this high potential point is higher than that of the heating pipelines on both sides, then this high potential point is the burial position of the fixed pier.

[0008] Step 3: Use the transient electromagnetic detector to measure the induced electromotive force again on both sides of the heating pipeline. If high induced electromotive force positions can be measured on both sides and can form a straight line with this high potential point in Step 2, then this high potential point in Step 2 should be the break point of the external thermal insulation and anti-corrosion layer of the heating pipeline caused by the cross pipeline, rather than the burial position of the fixed pier.

[0009] Furthermore, the voltage applied to the heating pipeline at the handhole is not greater than 24V.

[0010] Furthermore, divide the measurement range into several segments, measure the potential difference between the two endpoints of each segment, and find the high potential point based on the potential difference.

[0011] Furthermore, the high potential point is measured using a buried metal pipeline external anti-corrosion layer detector.

[0012] Furthermore, use the transient electromagnetic detector to measure the induced electromotive force again at 1 - 3 meters on both sides of the heating pipeline.

[0013] Working principle:

[0014] Except for the fixed joint steel ring of the directly buried heating pipeline that cannot be anti-corrosively treated, all other parts need to be insulated and anti-corrosively treated. That is to say, only the fixed ring on the entire directly buried heating pipeline is grounded. The overflow current forms an electric potential field on the ground. The center position of the electric potential field corresponding to the ground directly above the fixed ring has the highest electric potential. According to this characteristic, by applying a current with a specific frequency to the pipeline, as long as the electric potential field formed by the overflow current of the pipeline on the ground is detected on the pipeline route and the center point of the highest electric potential is measured, the fixed joint can be accurately positioned.

[0015] Both the fixed joint and the break of the pipeline external anti-corrosion layer can cause the overflow of the current loaded in the pipeline. To eliminate misjudgment, transient electromagnetic detection and recheck of metal variable detection need to be carried out on the detected electric potential point position. There is no obvious increase at the break point of the external anti-corrosion layer. Due to the structural characteristics of the fixed steel ring and the steel reinforcement cage of the fixed joint at the fixed pier position, the transient electromagnetic detection shows an obvious characteristic of increased metal, and the transient electromagnetic image shows an obvious trapezoidal curve characteristic.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses the non-excavation geophysical exploration method. First, the high potential point is measured along the heating pipeline by the electrical inspection method to preliminarily locate the positions of the fixed joint and the break of the external thermal insulation and anti-corrosion layer. Then, through the transient electromagnetic method, the interference of the break of the external thermal insulation and anti-corrosion layer is excluded, and the burial position of the fixed pier is accurately positioned, with an accuracy rate of up to 100%.

[0017] The present invention uses a non-excavation geophysical exploration method to locate the placement position of fixed piers, without the need to excavate the road surface, saving time and effort, with low cost, which is conducive to quickly improving the pipeline data of directly buried heating pipelines and providing a reference basis for work such as pipe fitting replacement construction and emergency repair material preparation. Description of the Drawings

[0018] Figure 1 is a flowchart of an embodiment of the present invention;

[0019] Figure 2 is a graph of induced electromotive force of an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram for judging the damage points of the external thermal insulation and anti-corrosion layer of a heating pipeline caused by a cross pipeline in an embodiment of the present invention. Detailed Embodiments

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the drawings and specific embodiments.

[0022] An embodiment of the present invention provides a non-excavation geophysical exploration method for the position of fixed piers of directly buried heating pipelines, as Figure 1 shown, which includes the following steps: <(

[0023] Step 1: Apply a voltage of 24V to the heating pipeline at the manhole, and measure the potential values within 50 meters on the ground along the routing of the powered heating pipeline starting from the manhole. The electrical inspection method can measure the routing of heating pipelines of 2 kilometers or even farther. For the convenience of description, in this embodiment, a 50-meter-long routing of the heating pipeline is selected, and the 50-meter length is divided into 100 segments, 50 centimeters per segment. Measure the potential difference between the two endpoints of each segment, and find the high-potential point according to the potential difference. The high-potential point is measured by an underground metal pipeline external anti-corrosion layer detector.

[0024] Step 2: Place the transient electromagnetic detector at the high-potential point and measure the induced electromotive force of the heating pipeline. If the induced electromotive force at this high-potential point is higher than the induced electromotive forces of the heating pipelines on both sides of it, and a graph of induced electromotive force is obtained, as Figure 2 shown, then the placement position of the fixed pier is initially judged at this high-potential point. If the induced electromotive force at this high-potential point is basically the same as the induced electromotive forces of the heating pipelines on both sides of it, then this high-potential point is judged as a damage point of the external thermal insulation and anti-corrosion layer.

[0025] Step 3: Eliminate the interference of the damaged point of the outer insulation and anti-corrosion layer of the heating pipe caused by the cross pipe. Place the transient electromagnetic detector 2 meters on both sides of the heating pipe, the position corresponds to the high potential point of the buried position of the fixed pier determined in step 2, and measure the induced electromotive force again to obtain two induced electromotive force curves. If the position of the high induced electromotive force can be found in both induced electromotive force curves, and can be connected to the high potential point in step 2 by a straight line, as shown in Figure 2. Figure 3 As shown in the figure, induced electromotive force curve A is measured at the heating pipe, while induced electromotive force curves B and C are measured 2 meters on either side of the heating pipe. Therefore, the high potential point in step 2 should be the point where the insulation layer on the heating pipe is damaged due to the crossing pipe, not the buried location of the fixed pier.

[0026] As required, all buried heating pipes require external insulation and corrosion protection. Typically, the pipes are coated with a polyurethane insulation layer and a PE outer anti-corrosion layer to insulate them from the ground. The insulation between the pipe and the ground is only compromised if the outer insulation layer is damaged. To prevent creep, the anchors must be welded directly to the pipes, making insulation and corrosion protection impossible. This results in a lack of insulation between the pipe and the ground at the anchoring piers. When voltage is applied to the pipes, damaged anchoring piers and outer insulation layers can cause leakage to the ground, creating high potential points.

[0027] When voltage is applied to a pipeline, locations without or missing anti-corrosion insulation serve as current overflow points, where electricity will leak to the ground. Specifically, locations with damaged anchors and the outer insulation layer will leak to the ground. These overflow points are high-potential points, meaning their potential is higher than that of surrounding locations. The potential around these locations decreases with increasing distance from the overflow point, until it reaches zero. By accurately detecting the electric field overflowing from the pipeline, with the center of the field corresponding to the overflow point, the grounded anchor and damaged outer insulation layer can be located through this perpendicular relationship.

[0028] The transient electromagnetic detector transmits a changing magnetic field to the heating pipe, generating an induced electromotive force (EMF) and forming eddy currents, also known as a secondary electromagnetic field. The magnitude of the induced EMF is primarily influenced by the conductor's electrical impedance. Because the fixed piers use metal fixings and a large amount of rebar, their electrical impedance is lower than that of the heating pipe. The electrical impedance at the site of the damaged outer insulation layer is the same as that of the heating pipe itself. Therefore, by measuring the induced EMF, it is possible to identify the location of the damaged outer insulation layer.

[0029] There is also a very rare situation where the external thermal insulation and anti-corrosion layer of the heating pipeline is damaged due to the construction of other pipelines, such as natural gas pipelines, water pipes, etc. These intersecting pipelines will also cause the impedance at that location to become smaller. Therefore, the induced electromotive force is measured again on both sides of the heating pipeline. The impedance of the intersecting pipeline should be less than that of the ground. If a high induced electromotive force is measured, it can be determined that there is an intersecting pipeline.

[0030] The present invention has been described in detail through the embodiments above. However, the content described above is only an exemplary embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. The protection scope of the present invention is defined by the claims. All those who utilize the technical solutions described in the present invention, or those skilled in the art who are inspired by the technical solutions of the present invention, within the essence and protection scope of the present invention, design similar technical solutions to achieve the above technical effects, or make equivalent changes and improvements to the application scope, etc., should still fall within the scope of patent protection covered by the present invention.

Claims

1. A trenchless geophysical exploration method for the location of fixed piers of directly buried heating pipelines, characterized by: The following steps are involved: Step 1: Apply voltage to the heating pipe at the hand well, measure the potential value on the ground along the route of the energized heating pipe from the hand well, and measure the high potential point; Step 2: Use a transient electromagnetic detector to measure the induced electromotive force at the high potential point. If the induced electromotive force at the high potential point is higher than the induced electromotive force of the heating pipes on both sides, then the high potential point is the buried position of the fixed pier.

2. The trenchless geophysical exploration method for the fixed pier position of a directly buried heating pipeline according to claim 1, characterized in that: Step 3: Use the transient electromagnetic detector to measure the induced electromotive force again on both sides of the heating pipe. If the position of the high induced electromotive force can be measured and can be connected to the high potential point in step 2 in a straight line, then the high potential point in step 2 should be the point where the insulation and anti-corrosion layer on the outside of the heating pipe is damaged due to the cross pipe, rather than the buried position of the fixed pier.

3. The trenchless geophysical exploration method for the fixed pier position of a directly buried heating pipeline according to claim 1 or 2, characterized in that: The voltage applied to the heating pipe at the hand well shall not exceed 24V.

4. The trenchless geophysical exploration method for the fixed pier position of a directly buried heating pipeline according to claim 1 or 2, characterized in that: Divide the measurement range into several segments, measure the potential difference between the two endpoints of each segment, and find the high potential point based on the potential difference.

5. The trenchless geophysical exploration method for the fixed pier position of a directly buried heating pipeline according to claim 1 or 2, characterized in that: The high potential points are measured using a buried metal pipeline external anti-corrosion layer detector.

6. The trenchless geophysical exploration method for the fixed pier position of a directly buried heating pipeline according to claim 2, characterized in that: The induced electromotive force is measured again using a transient electromagnetic detector at 1-3 meters on both sides of the heating pipe.

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